Acid rain is a new phenomenon occurring since the past few decades. Rain reacts with the oxides of sulphur and nitrogen to form acids. Undoubtedly, this oxides come from the industrial as well as automobile emissions. Acid rain is thus created by industrial activities that pollute the air. 

The main sources are electric power plants that use the energy produced by burning coal to generate electricity. Most coal contain small amounts of sulphur, which is converted to sulphur dioxide when the coal is burned. This is a global problem which after devastating a large part of the northern hemisphere is now intruding into the industrial regions of the South. This versatile destroyer eats away the forests, acidifies fresh water sources, afflicts human beings, and, causes irreversible damage to monuments and buildings which stand as testimony of time and symbols of our culture and civilization of the yester years.

The rainwater turns acidic due to the gases emitted by industries and automobile exhausts. These gases react under the influence of oxidants, catalysts and sun’s radiation before dissolving into water droplets and ice crystals to form dilute acid solutions. These acid solutions fall to the earth as rain, snow, hail, dew and fog. A peculiarity of acid rain is that while the causative agents are emitted at one place, the acid rain falls at another.